do not use include_directories when calling find_package(OpenCV)

This is something that should be left to the user, that's the whole
point of OpenCV_INCLUDE_DIRS.

cmake/templates/OpenCVConfig.cmake.in

@@ -122,7 +122,6 @@ SET(OpenCV_LIB_COMPONENTS @OPENCV_MODULES_CONFIGCMAKE@)
 # ==============================================================
 SET(OpenCV2_INCLUDE_DIRS @OpenCV2_INCLUDE_DIRS_CONFIGCMAKE@)
 if(OpenCV2_INCLUDE_DIRS)
-  include_directories(${OpenCV2_INCLUDE_DIRS})
   list(APPEND OpenCV_INCLUDE_DIRS ${OpenCV2_INCLUDE_DIRS})
 
   set(OpenCV_ADD_DEBUG_RELEASE @OpenCV_ADD_DEBUG_RELEASE_CONFIGCMAKE@)